The specific aim of this proposal is to determine the role of oculomotor internuclear neurons in eye movements. These neurons, found in an around the oculomotor nucleus, project to several areas of the brain. The diversity of these projections suggests that oculomotor internuclear neurons may be involved in several activities including eye movements (vergence and optokinetic nystagmus), autonomic functions (pupillodilation), and coordination of such actions as blinking and combined eye and head movements. All of these movements, particularly vergence, pupillary reflexes and blinking, form an integral part of most neurological examinations. Since accurate diagnosis requires a full knowledge of the physiology and anatomy of the neurons controlling these movements, it is important to understand oculomotor internuclear neurons. The intracellular staining and recording experiments in alert and anesthetized animals outlined in this proposal will provide a physiological and morphological description of oculomotor internuclear neurons. Such information can elucidate the role of these neurons in eye movements, thereby aiding in neurological diagnosis and significantly advancing the overall objective of this research which is to determine the brainstem mechanisms underlying eye movements.